Glaucoma is an optical neuropathy associated with increased intraocular pressure. The mechanism of the disease is not fully understood. However, the most effective therapy appears to be reducing the intraocular pressure, for example using medication or implants. Further damage to the optic nerve is thus prevented or reduced.
One procedure that has been suggested is non-penetrating trabeculectomy, in which a portion of the sclera overlying the Schlemm's canal is removed, allowing aqueous humor to leave the eye. It is desirable to remove only part of the thickness of the sclera, preventing penetration into the eye. However, this procedure is difficult to perform with a knife.
U.S. Pat. No. 5,370,641 to O'Donnell, the disclosure of which is incorporated herein by reference, describes using an excimer laser to ablate the sclera overlying the Schlemm's canal and the trabecular meshwork. The laser spot size and treatment area are not described. This patent states that when a sufficient amount of the corneoscleral bed is removed, aqueous humor comes through the remaining ultra-thin Schlemm's canal and trabecular meshwork and the energy of the laser is absorbed by the out-flowing humor, creating a self-regulating end point.
However, even though many years have passed since this patent was issued, the method taught in the patent has not found wide-spread use, in spite of a great need in the art of treating Glaucoma, a disease for which there is no completely satisfactory treatment.